Relative Translation System

ABSTRACT

A relative translation assembly operable with a drive mechanism. The relative translation assembly can have a fixed support member, a translatable member supported by the fixed support member, and a translation guide portion to facilitate translation of the translatable member relative to the fixed support member. The translation guide portion can have a fixed translation member and a movable translation member. The movable translation member can be configured to maintain preload on the fixed and movable translation members and accommodate thermal expansion. The drive mechanism can be configured to cause translation of the translatable member relative to the fixed support member.

RELATED APPLICATIONS

This is a divisional application of U.S. application Ser. No.15/666,285, filed on Aug. 1, 2017, entitled, “Relative TranslationSystem,” which is a divisional of, and which claims priority to, U.S.patent application Ser. No. 14/446,079 filed Jul. 29, 2014, entitled“Relative Translation System,” each of which are incorporated byreference in their entirety herein.

BACKGROUND

Relative translation mechanisms are used in a wide variety ofapplications. For example, in an aircraft optical assembly, a focus cellmay be configured to support and translate an optical element, such as alens, to facilitate focusing electromagnetic radiation for an opticalsensor. In this application, a linear slide table with a ball screwdrive shaft is typically used to move the optical element relative tothe optical sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the invention will be apparent from thedetailed description which follows, taken in conjunction with theaccompanying drawings, which together illustrate, by way of example,features of the invention; and, wherein:

FIGS. 1A and 1B are example illustrations of a relative translationsystem in accordance with an example of the present disclosure.

FIGS. 2A and 2B are example illustrations of the relative translationsystem of FIGS. 1A and 1B, with a fixed support member omitted forclarity.

FIG. 3 is an end view of the relative translation system of FIGS. 2A and2B.

FIG. 4 is an example illustration of a drive mechanism in accordancewith an example of the present disclosure.

Reference will now be made to the exemplary embodiments illustrated, andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended.

DETAILED DESCRIPTION

As used herein, the term “substantially” refers to the complete ornearly complete extent or degree of an action, characteristic, property,state, structure, item, or result. For example, an object that is“substantially” enclosed would mean that the object is either completelyenclosed or nearly completely enclosed. The exact allowable degree ofdeviation from absolute completeness may in some cases depend on thespecific context. However, generally speaking the nearness of completionwill be so as to have the same overall result as if absolute and totalcompletion were obtained. The use of “substantially” is equallyapplicable when used in a negative connotation to refer to the completeor near complete lack of an action, characteristic, property, state,structure, item, or result.

As used herein, “adjacent” refers to the proximity of two structures orelements. Particularly, elements that are identified as being “adjacent”may be either abutting or connected. Such elements may also be near orclose to each other without necessarily contacting each other. The exactdegree of proximity may in some cases depend on the specific context.

An initial overview of technology embodiments is provided below and thenspecific technology embodiments are described in further detail later.This initial summary is intended to aid readers in understanding thetechnology more quickly but is not intended to identify key features oressential features of the technology nor is it intended to limit thescope of the claimed subject matter.

Although linear slide tables have been successfully utilized in focuscells for some time, increased performance demands on optical systems isrevealing the limits and weaknesses of the design. For example, existinglinear slide table/ball screw focus cell designs are over-constrained bythe slide table and ball screw. As a result, designers must accept therisk of increased friction and potential binding of the mechanism overrunout tolerances and thermal expansion mismatches of the slide tableand ball screw over an operating temperature range, incorporate extraclearance, or incorporate extremely tight tolerances in the design.Runout tolerances between the linear slide table and the drive axis cancreate runout binding, which can vary in severity across an operatingtemperature range due to thermal expansion, thereby affectingresponsiveness and repeatability due to the changing friction. Toaccount for runout binding, designs may either include oversized gaps,which results in less accurate alignment and “jitter” of the opticalelement, or very expensive, tight, machining tolerances. Thermalexpansion can also cause “boresight drift” over a temperature range,which can negatively impact performance of the optical system. Inaddition, linear slide tables rely on a drive shaft to provide at leastsome structural support and may exhibit non-symmetric stiffness aboutthe optical element, which can cause jitter of the optical element.Thus, focus cell performance can be enhanced by maintainingresponsiveness and repeatability while minimizing boresight drift andjitter.

Accordingly, a relative translation system is disclosed that cancompensate for runout tolerances, minimize negative thermal expansioneffects, and symmetrical support an optical element. In one aspect,drive mechanism structures are decoupled from structurally supportingthe optical element. The relative translation system can include arelative translation assembly and a drive mechanism. The relativetranslation assembly can have a fixed support member, a translatablemember supported by the fixed support member, and a translation guideportion to facilitate translation of the translatable member relative tothe fixed support member. The translation guide portion can have a fixedtranslation member and a movable translation member. The movabletranslation member can be configured to maintain preload on the fixedand movable translation members and accommodate thermal expansion. Thedrive mechanism can be configured to cause translation of thetranslatable member relative to the fixed support member.

A relative translation assembly is also disclosed. The relativetranslation assembly can include a fixed support member, a translatablemember supported by the fixed support member, and a translation guideportion to facilitate translation of the translatable member relative tothe fixed support member. The translation guide portion can have a fixedtranslation member and a movable translation member. The movabletranslation member can be configured to maintain preload on the fixedand movable translation members and accommodate thermal expansion.

In addition, a drive mechanism is disclosed. The drive mechanism caninclude a drive shaft having a threaded portion. The drive mechanism canalso include a bearing to facilitate rotation of the drive shaft. Thebearing can be configured to support the drive shaft and interface witha first structure. Additionally, the drive mechanism can include a drivemember engaged with the threaded portion of the drive shaft andconfigured to be fixed to a second structure to facilitate translationrelative to the threaded portion upon rotation of the drive shaft. Anangle of misalignment of the bearing can compensate for drive shaftrotational misalignment. A position of the drive member can beadjustable upon assembly to compensate for drive axis translationalmisalignment.

One example of a relative translation system 100 is illustrated in FIGS.1A and 1B. The relative translation system 100 is shown configured as afocus cell, where an optical element 103, such as a lens, is supportedand translatable in direction 104 to facilitate focusing electromagneticradiation for an optical sensor (not shown), such as may be used in anaircraft optical assembly. Although a focus cell is shown and describedthroughout the present disclosure, it should be recognized that a focuscell is only one exemplary embodiment of a relative translation system.Accordingly, a relative translation system as disclosed herein may be ofany suitable configuration and adapted for use in any suitableapplication, such as where precision translation is needed over asignificant temperature variation and/or in a vibration environment. Forexample, a relative translation system may be used in high poweredmedical equipment, robotics, and applications for vehicles or equipmentused in harsh environments.

The relative translation system 100 can comprise a relative translationassembly 101. The relative translation assembly can include a fixedsupport member 110, a translatable member 120 supported by the fixedsupport member 110, and a translation guide portion 130 to facilitatetranslation of the translatable member 120 relative to the fixed supportmember 110. The relative translation system 100 can also comprise adrive mechanism 102 configured to cause translation of the translatablemember 120 relative to the fixed support member 110.

With continued reference to FIGS. 1A and 1B, FIGS. 2A and 2B illustrateaspects of the translation guide portion 130, with the fixed supportmember 110 omitted in FIGS. 2A and 2B for clarity. The translation guideportion 130 can have a fixed translation member 131 a, 131 b, 132 a, 132b, 133 a and a movable translation member 133 b. The fixed translationmember 131 a, 131 b, 132 a, 132 b, 133 a can be coupled to, andsupported by, the fixed support member 110. The movable translationmember 133 b can be movably supported by the fixed support member 110.In one aspect, the movable translation member 133 b can be configured torotate and/or translate relative to the fixed support member 110. Forexample, the movable translation member 133 b can be coupled to a swingarm 134, which can be rotatably coupled to the fixed support member 110to provide rotation about an axis 105.

The translation guide portion 130 can also include a translation membersupport 121, 123 with interface surfaces 121 a, 121 b, 122 a, 122 b, 123a, 123 b configured to interface with the fixed and movable translationmembers 131 a, 131 b, 132 a, 132 b, 133 a, 133 b, respectively. Thetranslation member support 121, 123 can be of any suitableconfiguration, such as a rail, track, guide, etc., and may be coupled tothe translatable member 120 via a permanent coupling (i.e., integrallyformed, or non-removably coupled with the translatable member 120) or aremovable coupling. Alternatively, it should be recognized that atranslation member support may be coupled to a fixed support member andthat a translation member may be coupled to, and supported by, atranslatable member. The fixed and movable translation members 131 a,131 b, 132 a, 132 b, 133 a, 133 b and the interface surfaces 121 a, 121b, 122 a, 122 b, 123 a, 123 b can be configured for a rolling and/orsliding interface.

In one aspect, the translation guide portion 130 can provide adequatesupport and/or constraint of the translatable member 120 sufficient tofacilitate translation of the translatable member 120 without utilizingthe drive mechanism 102 for structural support and/or constraint of thetranslatable member 120. As a result, the drive mechanism 102 can servepurely as a means to exert a drive force to cause translation of thetranslatable member 120. The drive mechanism 102 can therefore be of anysuitable type or configuration to cause translation of the translatablemember 120, and can include an electric motor, a hydraulic ram, apneumatic ram, a lead screw, a drive train, or any other linear drivemechanism or device that can cause translation of the translatablemember 120. As described further hereinafter, separation of the drivemechanism 102 from structural support and/or constraint of thetranslatable member 120 can provide benefits to reliability, switchingspeed, motion precision over a long range of travel, and others.

In one aspect, the movable translation member 133 b can be configured tomaintain preload on the fixed and movable translation members 131 a, 131b, 132 a, 132 b, 133 a, 133 b. For example, a spring 135 supported bythe fixed support member 110 can provide a force to preload the fixedand movable translation members 131 a, 131 b, 132 a, 132 b, 133 a, 133b, such as by acting on a pin or plunger 136 in contact with the swingarm 134. The movement of the movable translation member 133 b canaccommodate thermal expansion over a temperature range, such as thermalexpansion of the translatable member 120, while maintaining preload onthe fixed and movable translation members 131 a, 131 b, 132 a, 132 b,133 a, 133 b without substantially increasing friction, load, or stresson the fixed and movable translation members.

The fixed and movable translation members 131 a, 131 b, 132 a, 132 b,133 a, 133 b can be located or positioned in any suitable manner withrespect to one another, the fixed support member 110, and/or thetranslatable member 120. For example, as illustrated, the fixed andmovable translation members 131 a, 131 b, 132 a, 132 b, 133 a, 133 b canbe arranged in pairs, with two pairs of fixed translation members 131a-b, 132 a-b configured to interface with the translation member support121, and a mixed pair of the fixed translation member and the movabletranslation member 133 a-b configured to interface with the translationmember support 123. This is one example of a translation memberconfiguration that can provide adequate support and/or constraint of thetranslatable member 120. Such an arrangement or configuration cantherefore provide a kinematic or semi-kinematic mounting scheme. In oneaspect, one of the fixed translation members 131 a, 131 b, 132 a, 132 bcan be omitted from the configuration illustrated to provide threepoints of contact with the translation member support 121 and preservethe same degree of constraint for the translatable member 120. In oneexample (not shown), a single fixed translation member can be configuredto support and constrain a translatable member at a bottom end of thetranslatable member and a single movable translation member can beconfigured to support and constrain the translatable member at a top endof the translatable member.

As illustrated in FIG. 3, the translation member supports 121, 123, andassociated fixed and movable translation members 131 a, 131 b, 132 a,132 b, 133 a, 133 b, can be located diametrically opposite one anotherabout a center of mass 106 of the translatable member 120 and attachedstructures (i.e., optical element 103). In other words, a plane 107defined by the locations of the translation member supports 121, 123,and associated fixed and movable translation members 131 a, 131 b, 132a, 132 b, 133 a, 133 b, can pass through the center of mass 106. In oneaspect, the plane 107 can include an optical axis of the lens 103, inthis case extending perpendicular to the view in FIG. 3 through thecenter of mass 106. In another aspect, the fixed and movable translationmembers 131 a, 131 b, 132 a, 132 b, 133 a, 133 b can interface with thetranslation member supports 121, 123 at a minimal distance from thecenter of mass 106. Such an arrangement or configuration cansymmetrically support the translatable member 120 and attachedstructures about the center of mass 106 to minimize or reduce themoments created due to dynamic loading (i.e., vibrations), which canminimize or reduce jitter of the lens thereby improving performance. Itshould be recognized that an optical axis can be offset from the plane107 or in any suitable orientation relative to the plane, such as toimprove packaging efficiency and/or meet space constraints.

In one aspect, the fixed and movable translation members 131 a, 131 b,132 a, 132 b, 133 a, 133 b can comprise one or more rollers, asillustrated in FIGS. 1A-3. A roller is any structure, feature, or devicethat rotates to facilitate relative translation of the translatablemember 120 and the fixed member 110, typically of a cylindrical and/orspherical configuration, such as a wheel. Accordingly, the interfacesurfaces 121 a, 121 b, 122 a, 122 b, 123 a, 123 b can be configured tointerface with rollers. In a particular aspect, an interface between aroller and an interface surface can be “line” contact, which can preventor minimize yielding of the interface surface due to shock that cancreate localized depressions in the interface surface, therebymaintaining smooth motion and motion precision capabilities.

A roller can include a bearing, such as a ball bearing and/or a rollerbearing, which can be configured as a radial and/or a thrust bearing. Abearing can have an angle of misalignment that is the maximum amount aninner bearing race can go off-axis relative to an outer bearing race. Inone aspect, a bearing can have an angle of misalignment between innerand outer races that can serve to maintain line contact between a rollerand an interface surface. For example, manufacturing tolerances can beselected such that the angle of misalignment can be sufficient tofacilitate line contact between a roller and an interface surface uponassembly and maintained during operation. The bearings can therefore“self-align” to maintain line contact, which can preserve smooth motionand motion precision capabilities even after high loading events, suchas shock.

In one aspect, the relative translation system 100 disclosed herein canbe minimally affected by thermal expansion. For example, temperaturevariations can cause misalignment due to coefficient of thermalexpansion (CTE) mismatch. With regard to a relative translation systemin accordance with the present disclosure, the only CTE mismatch may bedue to the thickness of the bearing inner and outer races, which aresmall thicknesses compared to other designs. In the case of a focuscell, this can minimize boresight drift or lens misalignment over atemperature range, which can substantially maintain lens position overthe temperature range. The relative translation system 100 can thusprovide consistent, reliable, and repeatable performance over a range oftemperatures and when subjected to high (i.e., shock) loads.

FIG. 4 is a schematic illustration of a drive mechanism 202. The drivemechanism 202 can include a drive shaft 240 having a threaded portion241. The drive mechanism 202 can also include a drive shaft supportbearing 250 to facilitate rotation of the drive shaft 240 about a driveaxis 208. The drive shaft support bearing 250 can be configured tosupport the drive shaft 240 and interface with a first structure 210,such as a fixed support structure of a relative translation system asdisclosed above. For example, an outer race 251 of the drive shaftsupport bearing 250 can be configured to interface with the firststructure 210 and an inner race 252 of the drive shaft support bearing250 can be configured to interface with a locating portion 242 of thedrive shaft 240. The locating portion 242 and the inner race 252 caninterface with one another in an interference, clearance, or slip fit.In addition, the drive mechanism 202 can include a drive member 260engaged with the threaded portion 241 of the drive shaft 240. The drivemember 260 can be configured to be fixed to a second structure 220, suchas a translatable member of a relative translation system as disclosedabove, to facilitate translation relative to the threaded portion 241upon rotation of the drive shaft 240. In other words, the interface ofthe drive member 260 and the threaded portion 241 can convert rotationalmotion of the drive shaft 240 about the drive axis 208 to linear motionof the drive member 260 in direction 204. Although the drive shaftsupport bearing 250 is illustrated as interfacing with a fixed structureand the drive member 260 is illustrated as being fixed to a movablestructure, it should be recognized that the drive shaft support bearing250 can interface with a movable structure and the drive member 260 canbe fixed to a fixed structure.

In one aspect, a position of the drive member 260 can be adjustable uponassembly relative to the second structure 220 to compensate for driveaxis translation tolerance or misalignment, which occurs when a driveaxis does not “line up” with a translating member and may result due tomanufacturing tolerances. To accommodate this, the second structure 220can have an opening 224 to receive the drive shaft 240 that issufficiently oversized to allow the drive member 260 to “float” forlateral adjustment and “centering” without interference between thedrive shaft 240 and the second structure 220. After being centered, thedrive member 260 can then be fixed to the second structure 220 via anysuitable means, such as a fastener 261, pin, rivet, weld, etc. In thismanner, compensation for “as-built” tolerances leading to misalignmentof the drive axis 208 can occur at assembly. In another aspect, an angleof misalignment of the drive shaft support bearing 250 can compensatefor angular misalignment or rotational tolerances of the drive shaft,which may result due to manufacturing tolerances, such as the roundnessand/or non-concentricity of drive shaft 240 features and/or aperpendicularity tolerance of the first structure 210 to bearing 250interface. The drive shaft 240 can therefore be prevented from bindingor increased resistance with the drive member 260 due to misalignmentand/or runout tolerances of the drive shaft 240, such as rotationaland/or translational tolerances, by a one-time adjustment of the drivemember 260 and taking advantage of the angular misalignment of the driveshaft support bearing 250. This can facilitate manufacture of the drivemechanism 202 with more relaxed tolerances than would otherwise bepossible, which can reduce costs.

The drive mechanism 202 can also include a bearing 270 configured tointerface with the first structure 210 proximate the drive shaft supportbearing 250. For example, an outer race 271 of the bearing 270 can beconfigured to interface with the first structure 210. The bearing 270can have a clearance or loose slip fit for the drive shaft 240 extendingthrough an inner race 272 of the bearing 270. In one aspect, the driveshaft 240 can have a reduced diameter portion 243 to provide theclearance or loose slip fit with the bearing 270. Thus, the bearing 270may have no contact with the drive shaft 240. The bearings 250, 270 caneach have a rolling element 253, 273, respectively, which can comprise aball, roller, or other suitable bearing rolling element. The bearings250, 270 can also be configured as radial and/or thrust bearings.

In addition, the drive mechanism 202 can include a spring 280, such as aspring washer, configured to act on the inner race 272 of the bearing270 to facilitate preload of the bearings 250, 270. For example, thedrive shaft 240 can include a spring interface feature 244 to interfacewith the spring 280. The spring interface feature 244 can comprise alocally increased diameter portion of the drive shaft 240. A fastener281, such as a nut, can be threaded onto a threaded feature 245 of thedrive shaft 240 to preload the spring 280 and the bearings 250, 270. Atool interface feature 245, such as a hole, can be used to interfacewith a tool to resist rotation of the drive shaft while the fastener 281is rotated to apply preload. The drive shaft support bearing 250 cantherefore serve to locate and support the drive shaft 240 and thebearing 270 can serve to reduce rotating friction of the spring 280. Thelow friction provided by the bearing 270 for the spring 280 can provideperformance benefits, such as repeatability of lens adjustment when thedrive mechanism 202 is incorporated in a focus cell.

In one aspect, the drive shaft 240 can have a mid portion 246 configuredto provide flexibility sufficient to accommodate a misalignment and/orrunout tolerances of the drive shaft 240. For example, the mid portion246 can have a length 247 and a diameter 248 configured to flex inresponse to forces tending to bind and/or increase friction of thethreaded portion 241 and the drive member 260 while transferring torquesufficient to cause relative translation of the first and secondstructures 210, 220. The flexibility of the mid portion 246 cantherefore compensate for any remaining problems due to part and/orassembly tolerances.

By preventing or minimizing any binding or increased friction betweenthe drive shaft 240 and the drive member 260 due to misalignment orrunout tolerances, the drive mechanism 202 can be configured to simplyexert a drive force to cause translation of the second member 220without providing any structural support for the second member 220.Thus, the second member 220 can be structurally supported andconstrained for linear motion in direction 204 independent of the drivemechanism 202. This separation of the drive mechanism 202 fromstructural support and/or constraint of the second member 220 canprovide benefits to reliability, switching speed, and motion precisionover a long range of travel.

In one aspect, the drive mechanism 202 can include a backlashcompensation mechanism 263. The backlash compensation mechanism 263 cancomprise a nut 264 threaded onto the threaded portion 241 and coupled tothe drive member 260 via a pin 265 or other suitable fastener. A spring266 between the drive member 260 and the nut 264 can preload the nut264. Threads of the nut 264 can cooperate with threads of the drivemember 260 to remove backlash with the threads of the threaded portion241.

In an alternate example (not shown), the backlash compensation mechanism263, the bearing 270, and the spring interface feature 244 can beomitted. In this case, the spring 280 could contact and extend betweenthe inner race 252 of the drive shaft support bearing 250 and the drivemember 260, which could preload the drive member 260, as well as thedrive shaft support bearing 250, to prevent or eliminate backlashbetween the threads of the drive member 260 and the threaded portion 241of the drive shaft 240.

The drive mechanism 202 can also include a motor 290 coupled to thedrive shaft 240. For example, the motor 290 can be coupled to the driveshaft 240 via a drive train comprising one or more gears 291, 292, achain, a belt, and/or a pulley. The drive shaft 240 can include a driveinterface portion 249 to facilitate coupling with the motor 290, such asby interfacing with the gear 292. The motor 290 can be an electric motoror any other suitable motor for imparting torque to the drive shaft 240.In one aspect, the motor 290 can be coupled to and supported by thefirst structure 210.

It is to be understood that the embodiments of the invention disclosedare not limited to the particular structures, process steps, ormaterials disclosed herein, but are extended to equivalents thereof aswould be recognized by those ordinarily skilled in the relevant arts. Itshould also be understood that terminology employed herein is used forthe purpose of describing particular embodiments only and is notintended to be limiting.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, appearancesof the phrases “in one embodiment” or “in an embodiment” in variousplaces throughout this specification are not necessarily all referringto the same embodiment.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary. In addition, various embodiments and example of the presentinvention may be referred to herein along with alternatives for thevarious components thereof. It is understood that such embodiments,examples, and alternatives are not to be construed as de factoequivalents of one another, but are to be considered as separate andautonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. In thedescription, numerous specific details are provided, such as examples oflengths, widths, shapes, etc., to provide a thorough understanding ofembodiments of the invention. One skilled in the relevant art willrecognize, however, that the invention can be practiced without one ormore of the specific details, or with other methods, components,materials, etc. In other instances, well-known structures, materials, oroperations are not shown or described in detail to avoid obscuringaspects of the invention.

While the foregoing examples are illustrative of the principles of thepresent invention in one or more particular applications, it will beapparent to those of ordinary skill in the art that numerousmodifications in form, usage and details of implementation can be madewithout the exercise of inventive faculty, and without departing fromthe principles and concepts of the invention. Accordingly, it is notintended that the invention be limited, except as by the claims setforth below.

What is claimed is:
 1. A drive mechanism, comprising: a drive shafthaving a threaded portion; a bearing to facilitate rotation of the driveshaft, the bearing being configured to support the drive shaft andinterface with a first structure; and a drive member engaged with thethreaded portion of the drive shaft and configured to be fixed to asecond structure to facilitate translation relative to the threadedportion upon rotation of the drive shaft, wherein an angle ofmisalignment of the bearing compensates for drive shaft rotationalmisalignment, and wherein a position of the drive member is adjustableupon assembly to compensate for drive axis translational misalignment.2. The drive mechanism of claim 1, further comprising a backlashcompensation mechanism.
 3. The drive mechanism of claim 1, furthercomprising: a second bearing configured to interface with the firststructure proximate the first bearing, the second bearing havingclearance for the drive shaft extending therethrough; and a springconfigured to act on an inner race of the second bearing to facilitatepreload of the first and second bearings.
 4. The drive mechanism ofclaim 1, wherein the first structure comprises a fixed support of arelative translation system, and wherein the second structure comprisesa translatable member of the relative translation system.